Metal plates are normally bent within a long gap. The bending means generally obtains its driving power by means of a hydraulic cylinder or some other mechanism, and since the driving power is brought either from one point or a few points, the apparatus must be fairly rigid and stable. For this reason the apparatus is usually expensive to manufacture. The deflection of the apparatus usually obeys a generally known rule, which is proportional to the third power of the span length. Similarly, the thickness of structure has the same effect when the profile is constant. A plate-bending machine with holding jaws and a pivotable forming tool is known e.g. from German application publication 4343123 and from German application publication 2248679 corresponding to U.S. Pat. No. 3,815,393.
Swiss patent 620609 corresponding e.g. to U.S. Pat. No. 4,181,002 introduces a plate-bending device in which bending against a counter element is brought about by a forming member that is mounted for rotational movement in a housing of a mounting element and forms jaws that bend the plate edge against the counter element. The rotational movement of the forming member is brought about by moving the mounting element towards the counter element by a hydraulic cylinder. The device is a tool that is transferred manually in a direction parallel with the plate edge.